1. Field of the Invention
The present invention relates to an improvement in a curved belt conveyor.
2. Description of the Prior Art
FIG. 33 shows a conventional curved conveyor. The curved conveyor is composed of an endless curved belt 100 formed in an approximately conical shape and disposed between rollers 101 and 102 which are set at a predetermined angle in an approximately L-shaped arrangement in a plan view, thereby forming an approximately circular carrying track in a plan view. In the curved belt conveyor thus constituted, when the belt 100 is driven, a force F1 acts in the tangential direction of the circle having the turning center O of the belt 100 and at the same time a force F2 acts to move the belt 100 towards the turning center O.
The conventional curved belt conveyor, therefore, is constituted such that the belt is supported, along the outer peripheral edge, with a number of supporting mechanisms, such as beads and guide rails, chains, rollers, etc., for rotatably supporting the outer peripheral section of the belt, receiving the force F2 acting to move the belt towards the center of turning as described above and transmitting a driving power from a driving power source to drive the belt (Japanese Utility Model Laid-Open No. Hei 5-42211 and Japanese Utility Model Publication No. Sho 58-34082). It is, however, demanded to improve the above-described curved belt conveyor by obviating such disadvantages as troublesome maintenance, an increase in noise, and an increase in cost likely to be caused by the use of complicated supporting mechanisms along the outer peripheral section of the belt.
Furthermore, in the curved belt conveyor, because the rollers 101 and 102 supporting both ends of the curved belt are formed in a conical shape with relation to the peripheral speed of the belt, both ends of the carrying track are also formed conical. Consequently, large-diameter rollers are used in a junction with another conveyor, particularly on the outer peripheral side of the carrying track, forming a big difference in level at the junction section on the outer peripheral side of the carrying track, resulting in such a trouble as a shift or fall of loads and accordingly unsmooth transfer, particularly in carrying small, light-weight materials, at the junction section.
Some conventional curved belt conveyors so far developed are provided with a number of small cylindrical rollers, at both ends of the conveyor, continuously in the direction of the axial center to decrease the difference in level at junctions at both ends of the conveyor. It is, however, understood that because of a difference in the peripheral speed of the curved belt, the force F2 that acts to move the belt towards the center of turning increases.
To obviate the disadvantage stated above, there has been developed a curved belt conveyor as has been disclosed in Japanese Patent Laid-Open No. Hei 7-277436, in which no support mechanism is provided to support the outer peripheral edge section of the conveyor belt, but guide rollers are employed to support the inner peripheral edge of the curved belt from the inside while receiving the force F2 which acts to shift the belt towards the center of turning.
The curved belt described above is provided, in the thick inside structure of the belt, with a tough material which extends in the direction of width of the belt to increase belt strength in the direction of width, thereby preventing bend and deformation in the direction of width of the belt.
However, the force F2 which moves the curved belt towards the center of turning as described above tends to increase with an increase in the belt width; therefore the curved belt, though usable within a narrow range of belt width, cannot withstand the increase in the belt width, resulting in such a symptom of deformation as bulging at the central part of the belt.
The bulging of the above-described conveyor belt will give an adverse effect to loads if a difference in level at a junction at either end of the conveyor is reduced and small, short, light-weight pieces can be carried and transferred. That is, the curved belt conveyor described above is effective only for the use of a narrow belt.
In the meantime, the Japanese food industry is speeding up the introduction of the hazards analysis and critical control points (HACCP) that have been proposed in the U.S.A. for the purpose of preventing pathogenic bacteria such as O-157. In the case of a belt conveyor system used in food processing facilities, sanitary controls conforming to the HACCP are under consideration.
For example, to keep the belt conveyor hygienically clean, it is desirable to regularly remove, and carefully wash and sterilize the belt conveyor and the belt itself in order to prevent propagation of various germs. In some straight belt conveyors that have been developed, the end section of the conveyor is raised to enable easily reducing the belt tension(Japanese Utility Model Publication No. Hei 5-33459). In the curved belt conveyor, however, since the support mechanisms are extremely complicated as previously described, even a skilled operator needs considerable time to slacken the curved belt, often being forced to do troublesome work at the time of washing and sterilizing operation.
Also, in some conveyor lines using the curved conveyor, the direction of conveyance for carrying loads on the curved conveyor is not limited to one definite direction, and is sometimes required to be reversed. The curved conveyor, therefore, is required to have a function capable of easily reversing the direction of drive.
It is, therefore, an object of the present invention to provide a curved belt conveyor as described above that can realize, by the use of a simple driving mechanism, a curved belt conveyor with a wide belt capable of minimizing a difference in level at junctions at both ends of the conveyor, and furthermore is equipped with the function that facilitates mounting and removal of the curved belt.